A few related bug-fixes/refinements

* A patch to make sure that constraints on bones that point to
    external objects are evaluated correctly (and that the bones that
    depend on these bones are evaluated correctly, etc, ad nauseum).
    This addresses some of intrr's issues (the blender-related ones,
    that is).

  * Make sure that deformed displists are updated when the user
    manipulates any of the constraint buttons.

  * Added a nice little function, ik_chain_looper(), that executes a
    callback for every bone in an IK chain.

source/blender/src/buttons_object.c

@@ -731,8 +731,6 @@ static uiBlock *add_constraintmenu(void *arg_unused)
 
 void do_constraintbuts(unsigned short event)
 {
-	clear_object_constraint_status(OBACT);
-
 	switch(event) {
 	case B_CONSTRAINT_CHANGENAME:
 		break;
@@ -860,6 +858,9 @@ void do_constraintbuts(unsigned short event)
 	default:
 		break;
 	}
+
+	clear_object_constraint_status(OBACT);
+	make_displists_by_armature (OBACT);
 }
 
 static void object_panel_constraint(void)